/**

* Copyright 2013 Ronald W Hoffman

*

* Licensed under the Apache License, Version 2.0 (the "License");

* you may not use this file except in compliance with the License.

* You may obtain a copy of the License at

*

* http://www.apache.org/licenses/LICENSE-2.0

*

* Unless required by applicable law or agreed to in writing, software

* distributed under the License is distributed on an "AS IS" BASIS,

* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

* See the License for the specific language governing permissions and

* limitations under the License.

*/

package JavaBitcoin;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.nio.ByteBuffer;

import java.util.List;

/**

* <p>The 'merkleblock' message is sent in response to a 'getdata' block request

* and the requesting peer has set a Bloom filter. In this case, the response is just the

* block header and a Merkle branch representing the matching transactions.</p>

*

* <p>MerkleBlock Message</p>

* <pre>

* Size Field Description

* ==== ===== ===========

* 4 bytes Version The block version number

* 32 bytes PrevBlockHash The hash of the preceding block in the chain

* 32 byte MerkleRoot The Merkle root for the transactions in the block

* 4 bytes Time The time the block was mined

* 4 bytes Difficulty The target difficulty

* 4 bytes Nonce The nonce used to generate the required hash

* 4 bytes txCount Number of transactions in the block

* VarInt hashCount Number of hashes

* Variable hashes Hashes in depth-first order

* VarInt flagCount Number of bytes of flag bits

* Variable flagBits Flag bits packed 8 per byte, least significant bit first

* </pre>

*/

public class MerkleBlockMessage {

/**

* Builds the 'merkleblock' message

*

* @param peer Destination peer

* @param block Block to be sent to the peer

* @param indexList List of matching transaction indexes

* @return Message to be sent to the peer

* @throws IOException Unable to create the message data

*/

public static Message buildMerkleBlockMessage(Peer peer, Block block, List<Integer> indexList)

throws IOException {

List<Transaction> txList = block.getTransactions();

ByteArrayOutputStream outStream = new ByteArrayOutputStream(Block.HEADER_SIZE+txList.size()*32);

//

// The first 80 bytes are the block header

//

byte[] blockData = block.bitcoinSerialize();

outStream.write(blockData, 0, Block.HEADER_SIZE);

//

// Create the Merkle branch

//

List<byte[]> merkleTree = block.getMerkleTree();

MerkleBranch branch = new MerkleBranch(txList.size(), indexList, merkleTree);

branch.bitcoinSerialize(outStream);

//

// Create the message

//

byte[] msgData = outStream.toByteArray();

outStream.close();

ByteBuffer buffer = MessageHeader.buildMessage("merkleblock", msgData);

return new Message(buffer, peer, MessageHeader.MERKLEBLOCK_CMD);

}

}